The constantly increasing operational speeds of digital computers are creating a demand for corresponding increases in the data storage capacities of magnetic tape recording and reproducing systems, while maintaining the special requirements of high speed digital tape systems.
It is desirable that tape recording and reproducing systems for use as computer data storage devices provide high data transfer rates and perform a read check on all written data. Toward those ends, conventional tape systems typically employ methods of recording known as longitudinal recording, as illustrated in FIG. 1a, in which the tracks of data lie parallel to each other and parallel to the edges of the tape; or helical scan recording, as illustrated in FIG. 1b, in which the tracks of data lie parallel to each other but diagonal to the edges of the tape. The longitudinal recording method offers higher data transfer rates; but it would be desirable to obtain still higher data densities while retaining the advantages of the longitudinal recording method.
One limitation on track densities is crosstalk, which occurs when reading of data from one track is interfered with by data recorded on an adjacent track. Crosstalk is further exacerbated by error in head gap alignments. Some methods have been implemented to reduce this effect, such as leaving guard bands between tracks, or by using wider write head gaps. These methods, however, also tend to limit track densities, thereby limiting data densities.
A method of recording known as azimuth recording has been used in helical scan systems in order to decrease the effects of crosstalk and thus increase the track density of these systems. Azimuth recording results in a recorded track pattern in which the magnetization directions of adjacent data tracks lie at different azimuth angles to each other, as illustrated in FIG. 1c. This method greatly reduces inter-track crosstalk, enabling tracks to be placed closer together. The need for guard bands or wide write heads is thus reduced or eliminated. The helical scan method, however is subject to limited data transfer rates.